What Voltage Should My Alternator Be Putting Out? - Chevelle Tech
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post #1 of 21 (permalink) Old Apr 6th, 10, 9:15 PM Thread Starter
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What Voltage Should My Alternator Be Putting Out?

OK, I've been reading and reading. And I have rewired under my hood as described by Mark at MAD Electrical. I have a 94 amp internally regulated alternator (Ultima from Oreilly's) I have a 8 or 10 gauge wire going from the lug on the back of the alternator straight to my firewall mounted junction block. And I have the remote sensing wire from the internal regulator routed to this junction block as well. Everything else gets power from this junction block including my fuse panel and battery charging wire, which is run from the junction block to the positive lug of my remote solenoid. The theory is that I should be maintaining 14.2 or so volts to this junction block to provide an optimal amount of volts to all accesories. Well, it seems like everywhere I check voltage when the car is running I see 12.4 volts. I checked voltage at the alternator positive lug and 12.4 volts, then the junction block has 12.4 and the charging wire at the remote solenoid 12.4 and then at the battery 12.4. So it looks like the voltage is staying pretty stable, although my voltage meter inside is reading 12 volts flat. The only issue is that shouldn't all these voltage readings be at 14.2 volts? Am I missing something here? I mean everything is running fine, and I get a 12.6 volt reading from my battery when the car is off, but when I turn it on, I get a 12.4 volt reading from the alternator. Any help is greatly appreciated.
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post #2 of 21 (permalink) Old Apr 6th, 10, 9:29 PM
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Re: What Voltage Should My Alternator Be Putting Out?

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Originally Posted by adpostel View Post
and battery charging wire, which is run from the junction block to the positive lug of my remote solenoid.
I'm not sure about that configuration, but yes, your alternator should be putting out at least 14 volts. What RPM are you testing it at? Some of the hi-amp alternators don't do squat at idle. Try revving the engine up to about 2000 RPM and see what you measure at the battery.

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post #3 of 21 (permalink) Old Apr 6th, 10, 9:49 PM Thread Starter
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Re: What Voltage Should My Alternator Be Putting Out?

OH, I checked everything at idle today. But even when I'm inside and giving it gas, I don't see the volt meter move at all? I mean it goes to 12 volts when I turn the key forward, and then it obviously drops a little during cranking, then when started, it goes straight to 12 volts and stays......
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post #4 of 21 (permalink) Old Apr 6th, 10, 10:07 PM
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Re: What Voltage Should My Alternator Be Putting Out?

That does not sound right. I get about 14.7 at the back of my alternator when I first crank it up. It drops a little when things get hot and the battery tops off.

Do Chevelles not use the junction at the horn relay buss bar? As long as your sense wire is at the same location I wouldn't think it matters but was curious.

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post #5 of 21 (permalink) Old Apr 6th, 10, 10:40 PM
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Re: What Voltage Should My Alternator Be Putting Out?

every car that i've upgraded to a CS series alternator has put out 14.6 volts at the battery at idle with everything in the car turned on.
i always run a big cable directly from the big stud on the back of the alt directly to the + terminal on the battery, with no junction blocks getting in the way, then run a 10 or 12 gauge wire from the battery to a junction block to power the car. this is how GM started doing it in the mid 80's, and it works.

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post #6 of 21 (permalink) Old Apr 7th, 10, 12:19 AM Thread Starter
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Re: What Voltage Should My Alternator Be Putting Out?

So should I go swap that alternator out? I have a lifetime warranty on it, and it has literally less than 10 miles on it.
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post #7 of 21 (permalink) Old Apr 7th, 10, 1:56 AM
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Re: What Voltage Should My Alternator Be Putting Out?

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Originally Posted by adpostel View Post
OK, I've been reading and reading. And I have rewired under my hood as described by Mark at MAD Electrical. I have a 94 amp internally regulated alternator (Ultima from Oreilly's) I have a 8 or 10 gauge wire going from the lug on the back of the alternator straight to my firewall mounted junction block. And I have the remote sensing wire from the internal regulator routed to this junction block as well.
Did you convert from a externally regulated alternator? Your voltage readings indicate no output from alternator. You describe how you have wired the alternators BAT terminal (output) and terminal 2 (sensing) but how do you have terminal 1 (excite) wired?

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post #8 of 21 (permalink) Old Apr 7th, 10, 8:12 PM Thread Starter
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Re: What Voltage Should My Alternator Be Putting Out?

My terminal 1 (excite) wire is wired to a keyed ignition source outlet on the fuse box. But I went ahead and took the alternator to Oreilly's to get checked, and what do you know, it was bad. FAILED, FAILED, FAILED on all tests. So I'm picking up another one tomorrow, of course they didn't have it in stock.

So now I am wondering what effects, if any, this had when my motor was running. In other words, would I have been getting a weak spark out of the dizzy? Would this have affected my performance at all? Man I've been going round and round tuning this motor, and I am wondering now if this is gonna change anything? Would this make my motor run rich, due to a low spark? I know its a lot of questions, but any help would be appreciated.
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post #9 of 21 (permalink) Old Apr 8th, 10, 3:13 AM
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Re: What Voltage Should My Alternator Be Putting Out?

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Originally Posted by adpostel View Post
My terminal 1 (excite) wire is wired to a keyed ignition source outlet on the fuse box. But I went ahead and took the alternator to Oreilly's to get checked, and what do you know, it was bad. FAILED, FAILED, FAILED on all tests. So I'm picking up another one tomorrow, of course they didn't have it in stock.
Well, that most of the problem right there, you can not put a direct 12volt source to terminal 1, it has to have some resistance, either from the GEN light or a resistor wire. Factory idiot light cars have a GEN light with a resistor wire in parallel (to keep the alternator working if the GEN lamp burns out). Factory gauge cars only have the resistor wire. Personally, I would use the factory wiring for terminal 1. (brown wire that went to terminal 4 at external voltage regulator plug) If thats not possible, add a light bulb inline or a resistor.


Read the link below, its about a member on another board I helped who had his alternator wired like yours and went through several alternators, his was a CS130, but the principles are the same. Several solutions too.
http://www.camaros.net/forums/showthread.php?t=115803

Quote:
Originally Posted by adpostel View Post
So now I am wondering what effects, if any, this had when my motor was running. In other words, would I have been getting a weak spark out of the dizzy? Would this have affected my performance at all? Man I've been going round and round tuning this motor, and I am wondering now if this is gonna change anything? Would this make my motor run rich, due to a low spark? I know its a lot of questions, but any help would be appreciated.
Yes, it has some effect. As the battery runs down, voltage gets less and less.

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post #10 of 21 (permalink) Old Apr 8th, 10, 3:32 AM Thread Starter
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Re: What Voltage Should My Alternator Be Putting Out?

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Personally, I would use the factory wiring for terminal 1. (brown wire that went to terminal 4 at external voltage regulator plug) If thats not possible, add a light bulb inline or a resistor.
So are you saying here that I could basically wire in a socket and a light and that would provide the "resistance" needed to make the alternator work properly?" Is NO RESISTANCE, burning out something in the alternator, possibly?



This is quoted from the MAD ELECTRICAL Tech Pages, which is where I got my diagram for my underhood wiring,

"The voltage regulator in the photo above is used with the Delco 10SI and 12SI alternators. Notice that the voltage regulator above has two flat blade male terminals (see arrows). There is actually a third terminal of this voltage regulator, which is the ground at one of the three mounting screws. One of the two flat blade terminals is wired to an ignition switched ON/OFF source, and this circuit can also be used to operate a dash mounted warning light (The warning light is an option, not a requirement).

Thanks for the responses, its definitely a learning curve with these electrical gremlins.......
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post #11 of 21 (permalink) Old Apr 8th, 10, 3:43 AM
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Re: What Voltage Should My Alternator Be Putting Out?

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So are you saying here that I could basically wire in a socket and a light and that would provide the "resistance" needed to make the alternator work properly?"
Yes. Use a 194 bulb. A spare old side marker light will work. i did this one myself once.

Quote:
Originally Posted by adpostel View Post
Is NO RESISTANCE, burning out something in the alternator, possibly?
Yes, the regulator.



Quote:
Originally Posted by adpostel View Post
This is quoted from the MAD ELECTRICAL Tech Pages, which is where I got my diagram for my underhood wiring,

"The voltage regulator in the photo above is used with the Delco 10SI and 12SI alternators. Notice that the voltage regulator above has two flat blade male terminals (see arrows). There is actually a third terminal of this voltage regulator, which is the ground at one of the three mounting screws. One of the two flat blade terminals is wired to an ignition switched ON/OFF source, and this circuit can also be used to operate a dash mounted warning light (The warning light is an option, not a requirement).

Thanks for the responses, its definitely a learning curve with these electrical gremlins.......
The light is only a option, (cars came with or without a light) but resistance is mandatory, unless you like replacing alternators often.

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post #12 of 21 (permalink) Old Apr 8th, 10, 3:52 AM Thread Starter
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Re: What Voltage Should My Alternator Be Putting Out?

This is getting very interesting. I followed the MAD Electrical site due to everyone recommending the site. I wonder why there isn't much information on that number 1 terminal other than what I posted.
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post #13 of 21 (permalink) Old Apr 8th, 10, 4:01 AM
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Re: What Voltage Should My Alternator Be Putting Out?

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This is getting very interesting. I followed the MAD Electrical site due to everyone recommending the site. I wonder why there isn't much information on that number 1 terminal other than what I posted.
Because probably most everyone is using the factory wiring when converting (which will have the needed resistance) and most conversion instuctions use the factory wiring, including the one I post. My best guesss.


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post #14 of 21 (permalink) Old Apr 8th, 10, 6:28 AM Thread Starter
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Re: What Voltage Should My Alternator Be Putting Out?

OK, so I think I got it now. I will pick up my new alternator today, but since my underhood wiring isn't in stock form, it is in MAD Electrical form,(LOL),before I install it this time, I am going to take that exciter wire, and take it to a terminal on a spare light on my dash, the other terminal of that light will go to the keyed ignition source. This will be my idiot light, and I still have the volt meter. But an idiot light wouldn't hurt.

So basically, the exciter terminal on the internaly regulated alternator will always be "hot" when the alternator is charging. And when/if there is a problem, that terminal will go "negative" which in turn will light up my light on the dash, since now it will have a positive side from the fuse box, and the negative side at the alternator. Is this correct? And will this provide enough resistance to prevent burning out the new alternator? I think I'm getting this......
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post #15 of 21 (permalink) Old Apr 8th, 10, 1:30 PM
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Re: What Voltage Should My Alternator Be Putting Out?

Quote:
Originally Posted by adpostel View Post
OK, so I think I got it now. I will pick up my new alternator today, but since my underhood wiring isn't in stock form, it is in MAD Electrical form,(LOL),before I install it this time, I am going to take that exciter wire, and take it to a terminal on a spare light on my dash, the other terminal of that light will go to the keyed ignition source. This will be my idiot light, and I still have the volt meter. But an idiot light wouldn't hurt.
Correct. The only difference from factory is you don't have the bypass wire (the resistor wire in parallel with the bulb) If the bulb burns out, the alternator will quit charging, but you will know this from the voltmeter. You can always carry a extra bulb. Some models of powermaster alterntors can be wired as a 1 wire or a 3 wire. They will still charge (acting as a 1 wire) when the is no connection (such as a bulb burning out) to terminal 1. This is a option also.

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So basically, the exciter terminal on the internaly regulated alternator will always be "hot" when the alternator is charging. And when/if there is a problem, that terminal will go "negative" which in turn will light up my light on the dash, since now it will have a positive side from the fuse box, and the negative side at the alternator. Is this correct? And will this provide enough resistance to prevent burning out the new alternator? I think I'm getting this......
Correct, you got it.

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